Tag Archives: Meteorology

Amusing Monday: Words cannot dampen the essence of rain and snow

After I woke up one morning last week, I noticed that there was a thin layer of water coating the outdoor furniture and concrete around our house. I stepped outside and felt a fine mist in the air. I wondered, could this be the “scattered showers” that weather forecasters had talked about?

Surely, a “mist” is different from “showers,” which is also different from “rain.” But where does one end and another begin according to the experts? A little help from the glossary of the American Meteorological Society revealed that the proper term for a very light precipitation is “drizzle.”

My curiosity got the better of me, and I found myself going deeper and deeper into the terminology for precipitation, both official and unofficial, first in English and then in other languages.

Starting with the lightest precipitation, we have fog, which is not really precipitation, because the condensed water vapor is not falling. The same goes for mist, which consists of water droplets too fine to fall, so they drift about suspended in the air. To qualify as mist, the visibility must be greater than 1 kilometer, or 5/8 mile. Less than that is fog.

With drizzle, the water droplets are small — less than 0.5 millimeters (0.02 inches) — and they may appear to float on air currents, but they eventually fall to the ground. Mizzle, also known as Scotch mist, is a “combination of thick mist and heavy drizzle occurring frequently in Scotland and in parts of England,” according to the AMS glossary. Scotland also gives us Haar, a “cold mist coming from the ocean to the east of Scotland or England.”

Rain comes into play when the droplets are larger than 0.5 millimeter. The intensity of rain is defined as light rainfall when accumulation is no more than 0.10 inch per hour and never more than 0.01 inch in six minutes. Moderate rainfall is between 0.11 and 0.30 inch per hour and never more than 0.03 inch in six minutes. Heavy rainfall is more than 0.30 inch per hour or 0.30 inch in six minutes.

Showers, which have always had me confused, are derived from a cumuliform (vertical-forming) cloud and characterized by sudden onset and ending, usually with large droplets and accompanied by a rapid change in sky conditions. We can have rain showers, snow showers and sleet showers. There are also sprinkles, when the showers are light.

That brings us to the category of frozen precipitation. Freezing drizzle consists of tiny droplets that fall as liquid but freeze upon impact to form a frozen glaze. Freezing rain is basically the same with larger drops, while freezing fog forms the glaze when it comes into contact with exposed objects. The temperature of the water droplets for all three types is generally below freezing, so ice forms the instant they hit a surface. Again, fog is not really precipitation, but there is such a thing as ice fog, which occurs when the condensation freezes and hangs in midair.

When objects on the ground are cooler than the air but not below freezing, we get dew. When objects on the ground are cooler than the air and below freezing, we get frost. Like fog, these are not precipitation.

A snowflake forms when a multitude of ice crystals come together. When snowflakes grow heavy enough, they fall to the ground as snow. If they melt on the way down, we get rain. Sleet, which is frozen rain, forms when snow refreezes or when rain freezes on its way down. Graupel, an official term in the glossary, consists of snow particles surrounded by ice. Often called snow pellets, graupel is smaller than hail.

Hail is basically ice balls between 5 and 50 millimeters (0.2 to 2 inches) across, usually forming when the wind keeps the ice balls aloft to take on more and more moisture.

Besides all the types of precipitation, meteorologists have definitions for precipitation events. Besides showers, we have storms, in which winds rise to between 56 and 63 knots (64 to 72 mph). Snow flurries are technically snow showers, especially when snows are light and brief. Blizzards are at the opposite end of the spectrum, with heavy snow, low temperatures and strong winds.

Some events don’t fall within the standard definitions. “Cloudburst” and “downpour” are unofficial terms for heavy rain. A deluge generally refers to flooding, but it can mean an extended downpour. “Virga” is an official term, meaning precipitation that falls from a cloud, often in streaks, but evaporating before reaching the ground. A squall is a strong and sudden onset of wind, so a rain squall includes the element of rain.

A monsoon is a seasonal wind persisting in one direction. I thought it had something to do with rain, but that is only a recent interpretation. “Monsoon” is from the Arabic word “mausim,” meaning season. It was first applied to the winds over the Arabian Sea, blowing six months from the northeast and six months from the southwest. The word has become popular throughout the world, and monsoons in India are well known for their heavy rains.

I was amused by the ongoing debate over the word “thundershower.” For example, one TV viewer in Cleveland took local meteorologist Mark Johnson to task for using the term while talking about the weather on TV station WEWS, the local ABC affiliate.

“What meteorology school did Mark Johnson go to?” the viewer demanded to know. “The one in the bottom of a Cracker Jacks box???? WHAT in the world is a THUNDERSHOWER…? Is he insane, because he certainly is not funny. Annoying would be a more fitting description…. Time to teach the ole man some new, technically-correct terminology or just replace him altogether with someone who knows how to speak properly. Thank you.”

Mark Johnson took the comment in stride, saying he rarely uses the term — which does not officially exist — but he tries to connect with viewers who may invision “thunderstorm” as something severe.

“Technically,” he said, “every rumble of thunder is logged as a TRW, a thunderstorm. But who am I forecasting for? Other scientists or the general public? Is a light rain shower with a brief rumble of thunder really a storm to you? Probably not.

“Broadcast meteorology is about taking information that can be very technical, and changing it into language and images that viewers can more readily understand and, more importantly, use to plan their daily lives,” he added.

Personally, I see nothing wrong with thundershower, which conveys thoughts of a smattering of lighting and thunder amidst a moderate downpour. Officially, a thunderstorm is a local storm from a cumulonimbus cloud with lightning and thunder, usually with strong winds and heavy rain or hail. After all, the AMS glossary recognizes thundersnow, which is simply snow at the surface accompanied by lightning and thunder in the sky. It seems that the glossary simply needs a new definition for thundershower.

By the way, there is a great article in Grist magazine about new words coming about from the increasing number of extreme weather events. We now have “heat dome,” a huge high-pressure system that traps hot air; “rain bombs,” which are extreme downpours officially called wet microbursts (first video on this page); and “corn sweat,” a humid condition caused by planting lots of corn.

The Dutch have some interesting words for different kinds of weather, as described in “Dutch Review” magazine. Rory, a self-described “Irish guy,” provides us an interesting perspective on Irish weather in the second video on this page.

The third video provides an interesting perspective on the weather from Quark, the extra-terrestrial Ferengi character from “Star Trek: Deep Space Nine.”

The final video is from a list of 119 songs about rain posted by Flourish Anyway, with videos for most of those high on the list.

Amusing Monday: Umbrellas for James Bond, Bozo the Clown

They say it’s going to start raining steadily any day now and that we could be headed for rainy La Niña conditions this winter. So I thought it might be fun to pay tribute to the common — and especially the uncommon — umbrella.

The polite umbrella: Pull a string on the handle to squeeze through tight spaces or walk through crowds without poking someone.

I never knew people could be so creative with umbrellas, whose basic design goes back at least 2000 years when these devices were used by Chinese royalty. It remains unclear whether the first of these folding canopies was used to protect against sun or rain, according to a documented entry on Wikipedia.

Because umbrellas date back to antiquity, I guess I can’t search out the original patent, although it is said that the U.S. Patent Office has submissions with more than 3,000 plans to improve on the umbrella’s basic design. See the entry in Mental Floss.

As for etymology, the word “parasol” comes from the combination of “para,” meaning stop, and “sol,” meaning sun. However, if you want to stop the rain, then the French word “parapluie” comes into play. “Pluie” is a French word for rain, coming from the Latin “pluvial.” So, from now on, you can grab your parapluie when you go out into the rain if you would rather not carry an umbrella.

Raindrops pounding on a special conductive material in the umbrella fabric sets off LEDs to light the way. // Source: Yanko Design

Oddly enough, the word “umbrella” seems to come from the Latin “umbra,” which means shading or shadow, making “umbrella” synonymous with “parasol.” The Latin word for umbrella is “umbella.”

Contrary to common belief, the word “bumbershoot” does not come from Great Britain, and the British do not commonly use this word. Rather bumbershoot was American vernacular, first showing up in a dictionary in 1896, according to an article in World Wide Words.

Getting back to amusing umbrellas, you can go far afield in a search for a stylish, elaborate or finely decorated umbrella. You can seek out whimsy or prankishness in the design, such as in the umbrella with a squirt gun in the handle. You can also find items that meld the ancient with modern technology, such as a blue tooth device to answer the smart phone in your pocket or the miniature video projector for watching movies in the top of your umbrella.

A squirt gun in the handle of an umbrella can break up the monotony of the rain, which refills the pistol.

I’m not sure why I have never written about umbrellas, given the dozens of webpages and advertising sites devoted to the subject. I’ve selected five of the best websites for you to check out:

One video producer gathered up pictures of unusual umbrellas, including some not shown in the websites above. Complete with music, the video can be found on YouTube.

The video below is a demonstration of a specialized umbrella by a one-legged man named Josh Sundquist, who has the greatest attitude about life and problem solving. If you want to know why Josh doesn’t just wear rain gear, listen to what he has to say at 2:23 into the video. And check out Josh’s other videos, including a stand-up routine (no pun intended) about amputees on airplanes.

By the way, I have never owned an umbrella in my entire life, preferring to wear a rain jacket with a hood on most occasions, although rain pants sometimes come in handy. After looking at hundreds of cool umbrellas on the Internet, I think I will choose the perfect one for me. Then again, naaaaah!

Olympic Mountains deliver huge rainstorm on cue for researchers

Atmospheric scientists with NASA and the University of Washington chose a doozy of a week on the Olympic Peninsula to launch their four-month effort to measure precipitation and calibrate the super-sophisticated Global Precipitation Measurement (GPM) system.

The heart of the GPM system is an advanced satellite called the GPM Core Observatory, designed to measure rainfall and snowfall from space. If the system can be perfected, meteorologists and climatologists will have a fantastic tool for measuring precipitation where no ground-based instruments are located.

When the Doppler-on-wheels radar system arrived at Lake Quinault, skies were clear and the ground was dry.
When the Doppler-on-wheels radar system arrived at Lake Quinault, skies were clear and the ground was dry. // Photo: UW Atmospheric Sciences

To improve the satellite system, ground-based radar and other equipment were moved to remote areas of the Olympic Peninsula to take measurements (see video below). Meanwhile, aircraft flying above, below and inside the clouds were taking their own readings.

The program, called Olympex for Olympic Mountains Experiment, is impressive. Researchers chose the west side of the Olympics because that’s where storms arrive from the Pacific Ocean, laying down between 100 and 180 inches of rainfall each year. Sure, these folks were looking for rain, but did they really know what they were getting into?

Heavy rains arrived, raising the waters of Lake Quinault and nearly flooding the equipment.
Heavy rains arrived, raising the waters of Lake Quinault and nearly flooding the equipment on Friday. // Photo: UW Atmospheric Sciences

On Friday, a Doppler-on-wheels radar system was nearly flooded when between 4 and 14 inches of rain fell in various portions of the Quinault Valley, raising Lake Quinault by about six inches per hour over a period of several hours. For details, check out science summary for the day, which describes some of the measurements that were taken.

“We’re not just checking the satellite’s observations, the way you might double-check a simple distance measurement,” said project manager Lynn McMurdie in a news release from the University of Washington.

“We’re checking the connection between what the satellite sees from space, what’s happening in the middle of the storm system and what reaches the ground, which is what most people ultimately want to know,” McMurdle said. “So we’re not just improving the satellite’s performance — we’re learning how storm systems work.”

NASA’s “Precipitation Education” website explains how weather systems from the Pacific Ocean are experienced on land and how Olympex will sort things out:

“Large weather systems arrive in the Pacific Northwest from the ocean, and not all parts of the system are equal. The leading edge, called the pre-frontal sector, tends to be warmer and have steady rainfall. Next, the frontal sector marks the transition from the warmer air to the colder air and processes that produce rainfall are often most intense in this region. Finally the post-frontal sector, characterized by colder temperatures, will often bring showery rain and snow, and can produce large snowfall accumulations at higher elevations.

“The (Olympex) field campaign will be looking inside these storm clouds with ground radar and aircraft instruments to determine the accuracy of the GPM satellite constellation in detecting the unique precipitation characteristics in these different storm sectors.

“One of the aircraft will be flying through the clouds to make detailed measurements of raindrops, ice particles, and snowflakes as they are falling to Earth’s surface. Combined with data from the ground radars and the total amounts caught by the rain gauges and other instruments on the ground, scientists will be able to improve the computer models of precipitating clouds – the same types of computer models used to forecast the weather and project future climate.”

If you’d like to learn more about Olympex, check out these sources:

Global Precipitation Measurement Core Observatory NASA graphic
Global Precipitation Measurement Core Observatory // NASA graphic

We know pollen helps seed the trees — but what about clouds?

It was the clever headline that caught my attention: “April flowers bring May showers?”

But it was the latest research about pollen from the University of Michigan and Texas A&M that got me digging a little deeper and eventually arriving at the subject of clouds and climate change.

The bottom line is a possibility that pollen from trees and flowers can break apart during a rainstorm. The broken pieces can then float up into the air and seed the clouds for the next rainstorm.

Allison Steiner, associate professor of atmospheric, oceanic and space sciences at U-M, began exploring how pollen might seed the clouds after sweeping a layer of pollen off her front porch one morning and wondering what happens after the pollen drifts into the air.

Atmospheric scientists have never paid much attention to pollen. It is generally believed that pollen grains are too large to seed the clouds. Instead, most attention has been focused on man-made aerosols, such as particles from a coal-fired power plant. High in the atmosphere, the particles can encourage moisture in the air to condense, the initial step in the formation of rain.

But people with allergies may recognize that their symptoms grow worse after a rainstorm when the air begins to dry out. As Steiner explains in an M-I news release:

“When we were looking in the allergy literature we discovered that it’s pretty well known that pollen can break up into these tiny pieces and trigger an allergic response. What we found is when pollen gets wet, it can rupture very easily in seconds or minutes and make lots of smaller particles that can act as cloud condensation nuclei, or collectors for water.”

In a laboratory at Texas A&M, Sarah Brooks, a professor in atmospheric sciences, soaked six different kinds of pollen in water, then sprayed the moist fragments into a cloud-making chamber. Brooks and her colleagues found that three fragment sizes — 50, 100 and 200 nanometers — quickly collected water vapor to form cloud droplets, which are 10 times bigger than the particles. (It takes about 6 million nanometers to equal a quarter of an inch, so we’re talking about very small particles.) Brooks noted in a Texas A&M news release:

“Scientists are just beginning to identify the types of biological aerosols which are important for cloud formation. Our results identify pollen as a major contributor to cloud formation. Specifically, our results suggest that increased pollen could lead to the formation of thicker clouds and longer cloud lifetimes.”

The effect of cloud formation on global warming may be the most important mystery in climate science today, according to Jasper Kirby, a particle physicist who is leading a team of atmospheric scientists from 15 European and U.S. institutions. Consequently, the effect of aerosols on cloud formation must be equally important.

Clouds are known to cool the planet by reflecting sunlight back out to space, but they can also contain heat at night, so cloud formation plays a critical role in determining the rate of global warming. To better predict global warming, one has to better understand when and how clouds are formed at a “very fundamental level,” Kirby told reporter Rae Ellen Bichell in “Yale Environment 360.” Kirby added:

“By fundamental, I mean we have to understand what the gases are, the vapors, that are responsible for forming these little particles. And secondly, we have to understand exactly how quickly they react with each other and how they form the aerosol particles which … constitute the seeds for cloud droplets. And this process is responsible for half the cloud droplets in the atmosphere. It’s a very, very important process, but it’s very poorly understood.”

In the upper atmosphere, aerosols can directly reflect sunlight back into space. These include man-made aerosols from industrial pollution as well as natural aerosols, such as volcanic eruptions and desert dust and now possibly pollen. Check out NASA’s webpage on “Atmospheric Aerosols.”

Steiner, who is doing the pollen experiments, said understanding natural aerosols is critical to understanding climate change:

“What happens in clouds is one of the big uncertainties in climate models right now. One of the things we’re trying to understand is how do natural aerosols influence cloud cover and precipitation under present day and future climate.

“It’s possible that when trees emit pollen, that makes clouds, which in turn makes rain and that feeds back into the trees and can influence the whole growth cycle of the plant.”

For people more interested in the allergy aspects of this story, I found a website called pollen.com, which identifies a variety of ways that weather can affect pollen and thus allergies:

  1. A mild winter can lead to early plant growth and an early allergy season,
  2. A late freeze can delay pollen production in trees, reducing the risk of an allergic reaction,
  3. Dry, windy weather increases the spread of pollen and worsens allergy symptoms,
  4. Rain can wash pollen out of the air, reducing the risk of exposure to pollen, but
  5. Rain can also increase the growth of plants, especially grasses, increasing the pollen levels.

For a research report about how rain can break up pollen into smaller particles to trigger allergies, check out “Thunderstorm-associated asthma in Atlanta, Georgia” by Andrew Grundstein et al.

Overall, last year was very warm in Washington state

Last year, Washington state experienced its fifth-hottest year in 120 years of records maintained by the National Oceanic and Atmospheric Administration.

Meanwhile, records for average temperatures were broken in California, Arizona and Nevada, which lived through the highest averages in 120 years. Oregon had just one hotter year on record, while Idaho had three years with higher averages.

Temps

In Washington, the average temperature for the year was 48.4 degrees Fahrenheit, or 2.3 degrees above the long-term average. Hotter years were 1934 with 49.1 degrees; 1958, 49.0 degrees; 1992, 48.7 degrees; and 1998, 48.6 degrees. In 2004, the average temperature was 48.4, the same as this year.

California’s record high was based on an average temperature of 61.5 degrees, with Arizona at 62.3 and Nevada at 53.1. Oregon’s average of 49.5 degrees was exceeded only in 1934, when the annual average was 49.9 degrees.

For the nation as a whole, the average temperature in 2014 was tempered by some fairly extreme low temperatures in the Midwest, stretching into the Mississippi Valley. For the contiguous United States, the average temperature was 52.6 degrees — 0.5 degrees higher than the long-term average and tied with 1977 as the 34th warmest year on record, according to information from NOAA’s National Climatic Data Center.

Despite several months of record and near-record lows across the middle of the country, no state had an annual average that set a record for cold or even ranked among their five coolest years.

For the contiguous U.S. as a whole, last year was the 18th year in a row with an average temperature above the 120-year average. The last year with a below-average temperature was 1996. Since 1895, the temperature has risen an average of 0.13 degrees F per decade.

Precipitation across the contiguous U.S. was 30.76 inches last year, or 0.82 inch above the 120-year average. That makes it the 40th wettest year on record. On average, precipitation has increased by 0.14 inch per decade.

Precip

For Washington state, 2014 was the 16th wettest year on record. The average across the state was 48.73 inches, some 6.7 inches above the 120-year average.

Above-average precipitation occurred across the northern states last year, while the Southern Plains and Central Appalachians experienced below-average conditions.

Drought conditions continue in California, despite near-average annual precipitation. Exacerbating the problem is a three-year rainfall deficit combined with record-high temperatures this past year.

Meanwhile, drought conditions improved across the Midwest and Central Plains, though both improvements and declines were observed in various parts of the Southern Plains, Southwest and Southeast.

Washington state had its fourth-wettest spring on record, while Kansas had its third-driest spring. Other seasonal conditions can be found on the NCDC’s “National Overview” for 2014. The “Climate at a Glance” page can help you break down the data by state and time period.

Global data and analyses from NCDC are scheduled to be released tomorrow.